The story we’re trying to implement here is: as a user I want to search and filter houses so I can narrow my list of results.
To make this form and controller easier to handle we can use #form_for and
pretend that the search is an ActiveRecord object. This allows the form to show
fields that have been filled in or any errors on the search using existing Rails
infrastructure.
The trick is that we are not storing the search in a database; we are merely pretending to be an ActiveRecord object.
So we begin from the outside with a Cucumber test:
Feature: Searching and filtering houses
Scenario: Searching for a house by keyword
Given a house named "Glass houses" exists with a description of
"Don't throw rocks at me"
And a house named "Straw houses" exists with a description of
"Don't blow me down"
When I go to the house search page
And I fill in "Keyword" with "rocks"
And I press "Search"
Then I should see "Glass houses"
And I should not see "Straw houses"
Scenario: Filtering a house by price
Given a house named "Glass houses" exists that costs 25 thousand dollars
And a house named "Straw houses" exists that costs 10 thousand dollars
When I go to the house search page
And I select "20-30k" from "Price range"
And I press "Search"
Then I should see "Glass houses"
And I should not see "Straw houses"
From this we can write the controller test in a straight-forward manner using test spies in mocha:
class HouseSearchesTest < ActionController::TestCase
should_route :get, '/house_searches',
:controller => :house_searches,
:action => :index
context "GET to index with houses" do
setup do
@houses = [Factory.stub(:house), Factory.stub(:house)]
@search = HouseSearch.new
HouseSearch.stubs(:new).returns(@search)
@search.stubs(:results).returns(@houses)
@params = 'the params'
get :index, :house_search => @params
end
should_render_template :index
should "assign the houses to @houses" do
assert_received(@search, :results) {|expects| expects.with()}
assert_equal @houses, assigns(:houses)
end
should "assign the house search to @house_search" do
assert_received(HouseSearch, :new) {|expects| expects.with(@params)}
assert_equal @search, assigns(:house_search)
end
end
end
That gives us the interface we expect HouseSearch to conform to. We’d also typically write view tests for the form stating that it has the right action and fields and a submit button, but this blog post is too long already.
First it needs to pretend to be an ActiveRecord object:
class HouseSearchTest < ActiveSupport::TestCase
should "build a new HouseSearch with the expected params" do
params = {'keyword' => 'some keyword',
'price' => '20-30'}
house_search = HouseSearch.new(params)
params.each do |field, value|
assert_equal value, house_search.send(field)
end
end
should "handle nil on #new" do
assert_nothing_raised do
search = HouseSearch.new(nil)
end
end
should "produce nil on #id" do
search = HouseSearch.new
assert_nil search.id
end
should "produce true on #new_record?" do
search = HouseSearch.new
assert search.new_record?
end
end
Then it also needs to produce results when you ask it to:
class HouseSearchTest < ActiveSupport::TestCase
should "produce only houses with the keyword in the description when sent
#results for such a search" do
matching_house = Factory(:house, :description => 'foo')
nonmatching_house = Factory(:house, :description => 'bar')
results = HouseSearch.new('keyword' => 'fo').results
assert_all(results) {|house| house.description =~ /fo/}
end
should "produce only houses within the price range when sent #results
for such a search" do
matching_house = Factory(:house, :price => 10)
nonmatching_house = Factory(:house, :price => 50)
results = HouseSearch.new('price' => '30-100').results
assert_all(results) {|house| 30 <= house.price && house.price <= 100}
end
end
The last requirement to make the Cucumber pass are the view tests, as I mentioned. The outcome of the view tests (the implementation) looks like this:
<% form_for @house_search do |form| %>
<%= form.label :keyword %>
<%= form.text_field :keyword %>
<%= form.label :price %>
<%= form.select :price, [['20-30', '20-30k']] %>
<%= form.submit 'Search' %>
<% end %>
The key to all of this is the HouseSearch class that acts like an ActiveRecord
class just enough for us to use #form_for and to simplify our controller. An
extension to this is support for #errors, so that you can use in your form.
class HouseSearchTest < ActiveSupport::TestCase
should "produce an error on the :price field when sent #new with an
invalid price range" do
house_search = HouseSearch.new(:price => 'unknown')
assert_kind_of ActiveRecord::Errors, house_search.errors
assert_not_nil house_search.errors.on(:price)
end
end
Bonus source code
Some of you may want the resulting code. This isn’t as exciting but here it is anyway:
class HouseSearchesController < ApplicationController
def index
@house_search = HouseSearch.new(params[:house_search])
@houses = @house_search.results
end
end
class HouseSearch
attr_accessor :keyword, :price
def initialize(params)
params ||= {}
params.each do |key, value|
self.send("#{key}=", value)
end
end
def id
nil
end
def new_record?
true
end
def results
results = House.all
results = results.within_price_range(self.price) unless self.price.blank?
results
end
def errors
@errors ||= ActiveRecord::Errors.new(self)
@errors.add(:price, "must be a price range") unless self.price =~ /-/
@errors
end
end
